Early Phase 1
N=16
Calcitriol Monotherapy for X-Linked Hypophosphatemia
X-linked Hypophosphatemia · Hypophosphatemic Rickets · Hypophosphatemic Rickets, X-Linked Dominant
Bottom Line
View on ClinicalTrials.gov: NCT03748966 ↗Enrolled (actual)
16
Serious AEs
6.3%
Results posted
May 2026
Primary outcome: Primary: Change in Serum Phosphate in Adults and Children With XLH Between Baseline and 12 Months — 2.6; 2.1 mg/dl — p=0.318
Study Design & Population
- Study type
- Interventional
- Phase
- Early Phase 1
- Interventions
- Calcitriol (Drug)
- Age
- Pediatric, Adult, Older Adult · 3+ yrs
- Sex
- All
- Sponsor
- Massachusetts General Hospital
- Primary completion
- Mar 2025
Outcome Measures
| Outcome | Result | p-value |
|---|---|---|
| PRIMARY Change in Serum Phosphate in Adults and Children With XLH Between Baseline and 12 Months |
2.6; 2.1 | 0.318 |
| PRIMARY Change From Baseline in TmP/GFR in Adults and Children With XLH |
88.49; 89.08 | 0.114 |
| PRIMARY Rickets Score for Children With XLH |
1.6 | 0.215 |
| PRIMARY Change From Baseline in Nephrocalcinosis Grade |
1.15; 1.11 | 0.186 |
| SECONDARY Growth in Children With XLH |
-1.5 | 0.615 |
Summary
Children and adults with XLH recruited will be treated with calcitriol alone (without phosphate supplementation) for one year, during which the calcitriol dose will be escalated during the first 3 months of therapy. The investigators hypothesize that treatment of adults and children with XLH alone will improve serum phosphate levels and skeletal mineralization without causing an increase in kidney calcifications. The study will also examine if calcitriol therapy will improve growth in children.
Eligibility Criteria
Inclusion Criteria
- Clinical diagnosis of XLH with family history excluding male-to-male transmission, or positive genotype for PHEX mutation
- Serum PTH levels less than 1.5x the upper limit of normal
- Serum calcium levels less than 10.0 mg/dl
- eGFR >= 60 mL/min/1.73m2
- 25(OH) vitamin D level >= 20 ng/dL
Exclusion Criteria
- Known allergy to calcitriol
- Pregnancy or breast feeding
- Use of skeletally active agents such as bisphosphonates, teriparatide, SERMS, hormone replacement therapy and progesterone-only contraceptive agents (combination oral contraceptive use in premenopausal women is not an exclusion criterion).
- Unwilling or unable to stop therapy with calcitriol and phosphate therapy for two weeks prior to study
- Therapy with cinacalcet within the past two weeks
- Current use of growth hormone therapy
- Use of diuretics or medications that alter renal handling of mineral ions.
- Use of glucocorticoids for more than 14 days in the past 12 months with the exception of inhaled agents.
- History of malignancy except basal and squamous cell carcinoma of the skin.
- Significant history of psychiatric disease per DSM-5.
- Substance use disorder per DSM-5.
- Significant cardiopulmonary disease (unstable CAD or stage D ACC/AHA heart failure).
- Absence of laboratory values for serum calcium, phosphate and creatinine in the 24 months prior to enrollment.
Data sourced from ClinicalTrials.gov (NCT03748966). Outcome figures and adverse-event rates are extracted automatically from the registry's posted results and are provided for clinician reference, not as a substitute for the primary publication.